Plugins: what the Filmer needs as a plugin: carry, who sees a pose, a step in the camera cycle

PR 343's Filmer becomes a Luau plugin mod (kept in contrib/plugins/filmer) on general APIs instead of
its own C++:

- reskate.skater.carry: something held out in one or both hands and aimed, the body crouched (feet
  kept) and hunched over it, turned on the spot after it (Extension/Skater/carry.cpp, from the PR's
  filmer_hold.cpp, with tests)
- shown = "everyone" | "others" | "me" on skater.pose, reach and carry: the pose sent to the other
  players and the one drawn here are split when asked
- reskate.camera.cycle and the camera_cycle event: a plugin's camera as the last step of the camera
  height button's cycle, after first person
- reskate.session.nametags(false) holds the names over the other players off
- board.hide(bone, {others = true}) hides it in the board the others are sent too (a sent-pose filter)
- outfit.set takes hand wear slots; input.bind takes an action with no key of its own

Extension/Plugins/plugin_api.cpp

@@ -17,7 +17,7 @@ namespace {
 struct Event {
     std::string_view name, permission;
 };
-constexpr std::array<Event, 28> events{{
+constexpr std::array<Event, 29> events{{
     {"load", {}}, {"unload", {}}, {"tick", {}}, {"level_loaded", {}}, {"level_unloading", {}},
     {"trick_started", "events.tricks"}, {"trick_landed", "events.tricks"}, {"line_broken", "events.tricks"},
     {"draw", "overlay"}, {"player_joined", "session.read"}, {"player_left", "session.read"}, {"message", "net.session"},
@@ -25,7 +25,7 @@ constexpr std::array<Event, 28> events{{
     {"throwdown", "throwdowns"}, {"action", "input"}, {"screen_closed", "ui.screen"},
     {"board_landed", "events.skater"}, {"body_hit", "events.skater"}, {"bail_end", "events.skater"},
     {"physics_step", "events.physics"}, {"launch", "events.skater"}, {"trick_notes", "events.tricks"},
-    {"throwdown_ui", "throwdowns"}, {"touch", "session.skaters"}, {"touch_end", "session.skaters"},
+    {"throwdown_ui", "throwdowns"}, {"touch", "session.skaters"}, {"touch_end", "session.skaters"}, {"camera_cycle", "camera"},
 }};
 constexpr std::size_t maximum_key = 128;
 constexpr std::size_t maximum_command = 48;